Urinary tract infections are important causes of morbidity and mortality. During their lifetime, at least 12% of men and 10-20% of women experience a symptomatic acute urinary tract infection. Each year, over 100,000 patients are hospitalized with renal infections in the United States. The most common cause of these urinary tract infections is E. coli. The initial stage in the pathogenesis of E. coli urinary tract infections involves its adherence to the uroepithelial lining. Once adherent, the organisms encounter local bactericidal mechanisms that can defend the bladder mucosa. Only organisms that survive this host response can go on to produce urinary tract infections. Although much has been learned about the virulence factors of potentially uropathogenic E. coli, virtually nothing is known about the inherent antimicrobial mechanisms of the mammalian bladder. Our long term research objectives are to identify the molecules that enable the mammalian bladder to kill adherent E. coli and to ascertain whether deficiencies in such molecules contribute to the pathogenesis of urinary tract infections in predisposed or vulnerable individuals, such as women and the elderly. Because this general area has not been well explored to date, we have designed a sharply focussed effort to identify and localize antibacterial molecules in the rat bladder. Our preliminary studies have shown that we can recover potently bactericidal molecules from the rat bladder by rinsing it briefly with 1% acetic acid. The microbicidal molecules have been partially purified, and shown to be distinct from defensins, lysozyme and nuclear histones. The Specific Aims of this proposal are: 1. To identify and characterize proteins associated with the rat bladder wall mucosa that are bactericidal for E. coli ML-35p. 2. To analyze how various components of urine may influence the bactericidal properties of these endogenous bladder proteins. 3. To test the activity of these antimicrobial bladder proteins against a) E. coli strains freshly recovered from patients with urinary tract infections, b) E. coli strains that differ in attributes potentially associated with uropathogenicity, and against c) other common uropathogens, including, P. mirabilis, P. aeruginosa, S. epidermidis, enterococci, etc. 4. To immunolocalize the microbicidal proteins in the rat bladder. 5. To clone the microbicidal proteins from a rat bladder cDNA library, determine their complete primary amino acid sequences and ascertain their cellular sites of synthesis.